Caffeine Linked to Miscarriage

Aversion to Caffeine

According to the results of a recent study by the Kaiser Permanente Division of Research, high doses of daily caffeine during pregnancy may increase the risk of miscarriage. The risk remains the same whether the source of caffeine is from coffee, tea, soda, or hot chocolate. This was the first study to take into the account the aversion to caffeine that tends to occur alongside the pregnancy related symptoms of nausea and vomiting. In the past, such symptoms made it difficult to calculate the true effect of caffeine as regards the risk of miscarriage.

De-Kun Li, MD, Ph.D., an investigator with the Kaiser Permanente Division of Research and lead investigator of the study explained, "This study strengthens the association between caffeine and miscarriage risk because it removes speculation that the association was due to reduced caffeine intake by healthy pregnant women."

1063 pregnant women, staff members of Kaiser Permanente in San Francisco, participated in the study from October 1996-October 1998. These women were chosen for their participation in the study in light of the fact that they had never changed their consumption of caffeine during their pregnancies.

Two Cups or More

Women who consumed 2 or more cups of coffee, 5 12-ounce cans of caffeinated soda, or 200 mg of caffeine per day had twice the miscarriage risk of those women who consumed no caffeine. Women who consumed caffeine in amounts of less than 200 mg per day had more than a 40% risk for miscarriage.

The increased risk of miscarriage seems to be due to caffeine rather than to other chemicals in coffee and other beverages, since the effect is the same no matter the source of the caffeine.

Li comments that, "The main message for pregnant women from these findings is that they probably should consider stopping caffeine consumption during pregnancy because this research provides clearer and stronger evidence that high doses of caffeine intake during pregnancy can increase the risk of miscarriage."

It has been known for some time that caffeine crosses from the placenta to the developing fetus. The metabolic system of the fetus cannot metabolize this substance, leading to an adverse influence on cell development and decreased placental blood flow.

It was found that 16.8% of the women in the study, or 172 women miscarried. While 264 participants in the study (25 percent) drank no caffeinated beverages during pregnancy, 635 women (60 percent) reported 0-200 mg of caffeine intake per day, and 164 women (15 percent) consumed 200 mg or more of caffeine.